Methods for controlling deflection of a dynamic surface

ABSTRACT

A method of controlling deflection of a dynamic surface having a predetermined shape includes sensing a change in the predetermined shape of the dynamic surface, providing at least one piezoelectric actuator in communication with the dynamic surface for applying a counter force thereto, and activating the at least one piezoelectric actuator for applying the counter force to the dynamic surface for returning the dynamic surface to the predetermined shape.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a divisional application of U.S.patent application Ser. No. 09/425,594, filed Oct. 22, 1999, entitled“System and Method for Controlling Deflection of a Dynamic Surface.”

FIELD OF THE INVENTION

[0002] The present invention relates to controlling the shape of dynamicsurfaces and in particular to a system for controlling deflection of adynamic surface of a roll.

BACKGROUND OF THE INVENTION

[0003] In many industries, such as paper making, food processing, andtextiles, or any other industry that processes a web of material, rollsare used for various types of processing functions, and in manyinstances, the straightness of the roll is very important. For example,in a paper making assembly, roll deflection may adversely affect thequality of the product being produced because the surface of the paperreflects the shape of the roll over which it passes. Thus, it isdesirable for the rolls to be as smooth as possible and devoid of anyimperfections, deflections or variations so that the paper that isformed will be smooth and uniform. In addition to resulting in theproduction of inferior products, roll deflection may also result indamage to the roll itself or the machinery containing the roll. Thus,various attempts have been made to control the shape of rolls so as toavoid the problems described above.

[0004] U.S. Pat. No. 5,785,636 to Bonander discloses a roll having anouter surface made of a fabricated fiber matrix for strengthening andreinforcing the roll to minimize roll deflection.

[0005] U.S. Pat. No. 2,908,964 discloses a controllable convex rollhaving a pressure fluid chamber positioned between a roll axle and theroll shell. Adjusting the pressure in the pressure fluid chambercontrols deflection of the roll shell. However, the roll disclosed inthe '964 patent has a number of problems associated therewith includingsealing difficulties resulting in leakage of pressure fluid. Inaddition, the roll disclosed in the '964 patent has a relatively slowresponse time for changing the pressure of the pressure fluid, requiringabout 30 seconds to increase the pressure and about 10 seconds todecrease the pressure. As a result, the '964 patent system is unable torapidly respond to deflections in the roll and a considerable quantityof paper is wasted when such a roll is used in paper machines. Moreover,rolls having a convex exterior surface have a limited operating rangeand may obtain a uniform pressure across the exterior surface only at agiven load.

[0006] U.S. Pat. No. 5,197,174 to Lehmann discloses a controlleddeflection roll having a rotatable roll shell supported by a row ofhydraulic support elements. The support elements are connected withfluid lines that supply hydraulic fluid to the support elements forgenerating a pressure force at the exterior surface of the roll. The'174 patent also discloses a control device which controls the supply ofthe hydraulic fluid sent to each hydraulic support element. However, theLehmann system also has a relatively slow response time for correcting aroll deflection condition.

[0007] U.S. Pat. No. 4,301,582 to Riihinen discloses a system thatremoves deflections from a roll using magnetic forces. The roll has anon-rotating axle with ends having a load imposed thereat and acylindrical shell rotatably supported by bearings on the axle. Amagnetic core is formed in the axle and a plurality of pole shoes arespaced from the shell by an air gap. A plurality of electromagneticwindings, each wound on the core at one of the pole shoes, produce amagnetic compensating force field between the shell and the core forresponding to deflections in the roll.

[0008] U.S. Pat. No. 4,357,743 to Hefter, et al., discloses a controlleddeflection roll having a roll shell which is radially movable in atleast one plane in relation to a roll support. Position feelers orsensors are arranged at the ends of the roll shell for detecting one ormore deflections in the roll shell as a function of deviations from apredetermined reference or set point. The position feelers controlregulators operatively associated with pressure or support elementspositioned between the roll support and the roll shell so that the rollshell is maintained in the reference or set position.

[0009] U.S. Pat. No. 4,062,097 to Riinhinen discloses a roll havingmagnetic deflection compensation that may be used in the calender orpress section of a paper machine. The roll has an inner non-rotatingaxle and an outer shell surrounding and rotatable with respect to theaxle, the axle and the shell having a common axis. The axle includes aninner magnetic structure while the shell includes an outer magneticstructure that rotates together with the shell. These inner and outermagnetic structures cooperate to provide attraction between the shelland axle on one side of the above axis and repulsion between the shelland axle on the opposite side of the axis, thereby achieving deflectioncontrol and/or compensation.

[0010] Other techniques used to reduce the detrimental effects of rolldeflections include running process machinery at slower speeds in orderto avoid resonance problems, and using back-up roll systems to reducedeflections. Further techniques include floating a roll in a fluidmedium or using plural bearings for each bearing journal.

[0011] Therefore, there is a need to have a deflection control systemfor a roll that rapidly eliminates deflections in a roll. There is alsoa need for a deflection control system that effectively responds todeformations of the roll caused by various sources such as inducedvibrations, external loading and thermal loading. There is also a needfor a deflection control system that enables deflections to be inducedinto the roll for any purpose necessary.

SUMMARY OF THE INVENTION

[0012] The present invention addresses the above-identified problems byproviding a system and method for controlling deflection of a dynamicsurface. In its broadest sense, the present invention may be used toremove undesirable deflections from a dynamic surface or to activelycontrol the dynamic surface so as to conform the dynamic surface into adesired shape. The present invention may also be used to controlvibration of a dynamic surface. In preferred embodiments, the presentinvention may be used to control deflection of a dynamic surface on anyobject that rotates including, but not limited to, a roll that engages aweb, a gear, wheels and/or tires. In highly preferred embodiments, theinventive system includes at least one piezoelectric actuator incommunication with a roll for applying compression and tensile forces tothe roll so as to control roll deflection and/or force one or moresurfaces of the roll to assume certain shapes.

[0013] As is well known to those skilled in the art, piezoelectricelements may be used to covert electrical energy into mechanical energyand vice versa. For nanopositioning, the precise motion that resultswhen an electric field is applied to a piezoelectric material is ofgreat value. Actuators using this effect have changed the world ofprecision positioning. As used herein, a piezoelectric actuator means apiezoelectric device or element, or any electronic device that operatesin a similar fashion to a piezoelectric element such as an electromagnetor a magnetostatic device.

[0014] The present invention may be used for a broad range ofapplications whereby the system components move at various speeds. Forexample, the deflection control system of the present invention can beused when making a paper web moving at approximately 5000 feet/minute,when making textile materials moving at approximately 100-300feet/minute or when making paper maker's clothing (PMC) moving atapproximately 1-30 feet/minute.

[0015] In accordance with one aspect of the present invention, there isprovided a system for controlling deflection of a dynamic surface, suchas the exterior surface of a roll. As set forth herein, the term“dynamic surface” means any surface that may change with respect totime, regardless of whether the change occurs over 5-10 minutes or overa time period as small as one microsecond. However, as microtechnologyimproves and microprocessors operate at faster speeds, it iscontemplated that the present invention could be used for dynamicsurfaces that change over a period of time as small as 1 nanosecond. Thesystem preferably includes at least one sensor in communication with thedynamic surface for detecting the presence of a force on the dynamicsurface and generating a feedback signal proportional to the force. Asused herein, the term “force” includes any force to which the dynamicsurface may be subjected including pressure forces, compressive forces,tensile forces, resonance, vibrations, thermal action or other processforces. Moreover, the above-listed forces may be applied in anydirection with respect to the dynamic surface including directions thatare substantially perpendicular to the dynamic surface and directionsthat are substantially parallel to the dynamic surface. The system alsoincludes a controller in communication with the at least one sensor forreceiving the feedback signal from the sensor and generating an outputsignal responsive to the feedback signal. The magnitude of the outputsignal is generally proportional to the magnitude of the feedbacksignal.

[0016] The system also preferably includes at least one piezoelectricactuator in communication with the dynamic surface and in signalreceiving and sending communication with the controller for receivingthe output signal from the controller and applying a counter deflectingforce on the surface. The counter deflecting force applied by thepiezoelectric actuator is preferably responsive to the detection of adeflection in the dynamic surface of the roll, whereby the piezoelectricactuator exerts the counter deflecting force to remove the deflectionand return the dynamic surface to a preferred shape or configuration.The piezoelectric actuator may also be activated to apply a counterdeflecting force so as to force the dynamic surface into a preferredshape, such as a roll having a convex surface.

[0017] The application of piezoelectric elements to dynamic surfaces,such as the exterior surface of a roll, resolves the problem of rolldeflection in a much more efficient manner than is available with theexisting technologies described above. Piezoelectric actuators can applyforces independently, and in various combinations, compared to most ifnot all of the existing roll control methodologies. Piezoelectricactuators are extremely precise, allowing repeatable nanometer andsub-nanometer movements. In addition, piezoelectric actuators canproduce significant amounts of force over relatively small areas and arecapable of moving heavy loads of up to several tons. Moreover, theresponse time of piezoelectric elements is in the kilohertz range sothat they may be activated at very high frequencies. This is becausepiezoelectric elements derive their motion through solid state crystaleffects and have no moving parts. Finally, piezoelectric elementsrequire very little power and require no maintenance.

[0018] The at least one piezoelectric actuator preferably includes aplurality of piezoelectric actuators that are provided in contact withthe dynamic surface. The piezoelectric actuators are preferablypiezoelectric foils having a length of approximately 1 to 5 centimeters,a width of approximately 1 to 5 centimeters and a height of less than 1centimeter. As such, one piezoelectric actuator preferably covers anarea of approximately 1-25 cm². In other preferred embodiments,piezoelectric actuators of any size and/or dimension may be used. Thus,the present invention is not limited to using actuators of the size/typelisted above.

[0019] The present invention preferably applies a plurality ofpiezoelectric actuators in contact with the dynamic surface of a roll sothat relatively large controlling forces may be applied to the dynamicsurface. Because each piezoelectric actuator can be controlledseparately by the controller, it is possible to create virtually anytype of deflection or shape in the dynamic surface that is desired,thereby providing for unlimited performance possibilities not availablein prior art technologies.

[0020] In one preferred embodiment, the dynamic surface is preferablyprovided on a roll shell, such as a roll shell, secured over a rollsupport. The roll shell is preferably flexible and substantiallycylindrical, has an interior surface defining an inner diameter of theroll shell and an exterior surface defining an outer diameter of theroll shell. In certain preferred embodiments, the exterior surface ofthe roll shell includes the dynamic surface. The sensors andpiezoelectric actuators are preferably connected to the interior surfaceof the roll shell. However, in other embodiments, the sensors andpiezoelectric actuators may be connected to either the inner or exteriorsurface of the roll shell, or any combination thereof. In otherembodiments, the sensors are in communication with, but not in contactwith, the roll shell. In certain embodiments the roll is what iscommonly referred to as a non-coated roll, however, in other embodimentsthe roll may be a coated roll.

[0021] The roll shell preferably has a longitudinal axis and preferablyrotates about a central axis substantially parallel to the longitudinalaxis. The roll shell is desirably mounted on a roll shell support thatsupports rotation of the roll shell about the central axis thereof. Theroll shell support may include an axle mounted to an external supportstructure. The axle may rotate.

[0022] In certain embodiments, the counter deflecting force applied bythe piezoelectric actuators generates either a compressive force or atensile force on the dynamic surface of the roll shell. The compressiveand tensile forces are generally opposed to one another. In other words,the compressive forces compress the dynamic surface towards the centerof the roll shell while the tensile forces stretch the dynamic surfacetoward the ends of the shell. The piezoelectric actuators may be alignedto exert compressive and tensile forces in directions substantiallyparallel to or substantially perpendicular to the longitudinal axis ofthe shell. The piezoelectric actuators may also be aligned to applycompressive and tensile forces to the dynamic surface in a plurality ofvarious directions that are neither perpendicular to nor parallel to thelongitudinal axis of the shell.

[0023] The deflection control system of the present invention preferablyincludes a plurality of sensors in communication with the shell. Thesensors are designed for detecting and/or measuring the magnitude ofdeflecting forces acting upon the dynamic surface of the shell. Thesensors are preferably spaced apart from one another and interspersedbetween the piezoelectric actuators. In certain preferred embodiments,the piezoelectric actuators are aligned in rows over the interiorsurface of the shell and the sensors are interspersed between thepiezoelectric actuators. The rows of aligned piezoelectric actuators mayextend in directions substantially parallel to or perpendicular to thelongitudinal axis of the shell, or may extend in any number ofdirections between those that are substantially perpendicular and thosethat are substantially parallel to the longitudinal axis of the shell.The ratio of piezoelectric actuators to sensors is preferably about100:1. The sensor may be one of a wide variety of sensors including butnot limited to a piezoelectric element, a strain gauge, a laser used inconjunction with a reflective element, an optical device, a capacitivedevice and/or a magnetic device. In other preferred embodiments, theratio of piezoelectric actuators to sensors will vary. The ratio may be1:1, or the number of sensors may outnumber the number of piezoelectricactuators.

[0024] The deflection control system of the present invention alsopreferably includes a controller having a microprocessor and a memorydevice. The memory may have stored therein look-up tables, a controlstrategy algorithm and/or an adaptive feedback control strategyalgorithm. The controller is preferably designed for receiving feedbacksignals from the sensors. The controller then processes the feedbacksignals to determine whether signals indicate the presence of adeflection. If an undesirable deflection is detected at one or moreregions of the dynamic surface, the controller transmits output signalsto the piezoelectric actuators at those deflected regions for removingthe deflection(s) and/or changing the shape of the dynamic surface.

[0025] The particular type of output signal transmitted to eachpiezoelectric actuator determines whether a compressive force or atensile force is applied to the dynamic surface. For example, thecontrol strategy may be to keep the dynamic surface in a neutralcondition so that if a deflected region of the dynamic surface is undercompression, then an output signal transmitted to the piezoelectricactuator will activate the piezoelectric actuator to apply a tensileforce to the deflected region. On the other hand, if a deflected regionof the dynamic surface is under a tensile force, the output signaltransmitted to the piezoelectric actuator will activate thepiezoelectric actuator to apply a compressive force to the deflectedregion.

[0026] In certain preferred embodiments, the system for controllingdeflection of a dynamic surface may be utilized for a web supportstructure located between two rolls so as to support the web as itpasses by the web support structure. In these particular embodiments,the web support structure includes a supporting element having a websupport layer. The web support layer has a top surface including thedynamic surface and a bottom surface remote therefrom. The dynamicsurface is designed to engage the web passing thereover, such as a webof partially formed paper moving over the dynamic surface during a paperforming process. As set forth above, the control system of the presentinvention may also be used for processing textile materials and/or papermaker's clothing felts or any other process involving web handling. Inthese particular embodiments, the sensors and the piezoelectricactuators are provided in contact with the second surface of the websupport layer. However, in other embodiments, the sensors andpiezoelectric actuators may be in contact with either the first surfaceor the second surface or any combination thereof. The dynamic surface ofthe web support layer may be substantially flat or have an arcuatesection. In certain embodiments, the one or more sensors preferablydetermine the position of the dynamic surface in relation to thesupporting element for detecting the presence of a deflecting force uponthe dynamic surface.

[0027] In other preferred embodiments, a dynamic surface has apredetermined shape that is stored within the memory of the controller.In this embodiment, the system for controlling deflection of the dynamicsurface includes at least one sensor connected to the dynamic surfacefor sensing a change in the predetermined shape of the dynamic surfaceand generating a feedback signal proportional to a magnitude of thechange. The system includes a controller in communication with the oneor more sensors for receiving the feedback signal and generating anoutput signal in response thereto. The controller analyzes the one ormore feedback signals by comparing the feedback signals with data storedin the memory thereof. If necessary, the controller then generates oneor more output signals and transmits these output signals to thepiezoelectric actuators in contact with the dynamic surface. Uponreceiving the output signals, the piezoelectric actuators are activatedfor applying a counter deflecting force on the dynamic surface forreturning the dynamic surface to the predetermined shape. Once thedynamic surface has been returned to the predetermined shape, thesensors that detected the change in the predetermined shape would thengenerate feedback signals indicating that the dynamic surface was onceagain in the predetermined shape. As a result, the piezoelectricactuators remain inactive. The piezoelectric actuators remain inactiveuntil their activation is again necessary in order to return the dynamicsurface to its predetermined shape.

[0028] In still further embodiments, at least one mass overlies at leastone of the piezoelectric actuators. In these embodiments, at least oneof the piezoelectric actuators is sandwiched between the at least onemass and the interior surface of the shell. In certain applications,there is a need to operate rolls at a speed that coincides with theresonance of the roll. When operated at or near resonance, a roll'sdynamic response may cause detrimental effects on the roll itself, themachinery containing the roll and the process that the roll iscompleting. Using piezoelectric devices mounted between the roll (orother machine members) and a mass, and having the piezoelectric actuatorconnected to and controlled by a properly designed control device,vibrations in the dynamic surface of the roll can be reduced and/orcontrolled, thereby eliminating or reducing detrimental effects.Similarly, vibrations can be induced into rolls or other machine membersfor any purposes necessary.

[0029] In still further embodiments, a method of controlling thedeflection of a dynamic surface includes providing a dynamic surfacehaving a predetermined shape and providing at least one piezoelectricactuator connected to the dynamic surface for applying a counterdeflecting force thereto. For purposes of the present application, theterminology “counter deflecting force” means that the piezoelectricactuator will be activated to provide either a compression force or atensile force to the portion of the dynamic surface to which thepiezoelectric actuator is engaged. The method also includes sensing achange in the predetermined shape of the dynamic surface andtransmitting the feedback signal from the sensor to the controller. Thecontroller then generates an output signal that is proportional to thefeedback signal and transmits the output signal to the piezoelectricactuator. Upon receiving the output signal, the piezoelectric actuatoris activated for applying the counter force to the dynamic surface.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]FIG. 1A is a schematic side view of a prior art roll and matingroll engaging a web at a nip.

[0031]FIG. 1B is a schematic side view of another prior art rollengaging a web.

[0032]FIG. 2A is a sectional view of the prior art roll of FIG. 1A takenalong lines IIA-IIA.

[0033]FIG. 2B is a sectional view of the prior art roll of FIG. 1B takenalong lines IIB-IIB.

[0034]FIG. 3A shows a simplified view of the prior art roll of FIG. 1Ain a deflected position.

[0035]FIG. 3B shows a simplified view of the prior art roll of FIG. 1Bin a deflected position.

[0036]FIG. 4A is a schematic side view of a roll including a system forcontrolling deflection of the roll, in accordance with certain preferredembodiments of the present invention.

[0037]FIG. 4B is a fragmentary schematic side view of a roll, inaccordance with further preferred embodiments of the present invention.

[0038]FIG. 4C is a fragmentary schematic side view of a roll, inaccordance with still further preferred embodiments of the presentinvention.

[0039]FIG. 5 is a fragmentary top view of a the roll taken along linesV-V of FIG. 4A including a plurality of sensors and piezoelectricactuators in contact with the dynamic surface of the roll, in accordancewith certain preferred embodiments of the present invention.

[0040]FIG. 6 shows a fragmentary view, on an enlarged scale, of thedynamic surface of the roll shown in FIG. 5.

[0041]FIG. 7 shows a simplified sectional or fragmentary side view ofthe roll shown in FIG. 4A when the roll is deflected.

[0042]FIG. 8 shows a sectional view taken along lines VIII-VIII of FIG.7 when the roll is deflected.

[0043] FIGS. 9A-9D show a simplified view of the roll of FIG. 8 duringvarious stages of revolution of the roll.

[0044]FIG. 10 shows a simplified side view of the roll of FIG. 7 afterdeflection control system of the present invention has returned the rollto an undeflected state.

[0045]FIG. 11A is a schematic side view of a non-coated roll including asystem for controlling deflection of the roll, in accordance withfurther preferred embodiments of the present invention.

[0046]FIG. 11B is a schematic side view of a coated roll including asystem for controlling deflection of the roll, in accordance with stillfurther preferred embodiments of the present invention.

[0047]FIG. 12 shows a schematic side view of a system for controllingdeflection of a dynamic surface, in accordance with further preferredembodiments of the present invention.

[0048]FIG. 13A is a sectional view taken along lines XII-XII of FIG. 12,showing the dynamic surface of a web support layer in a deflectedposition.

[0049]FIG. 13B shows a sectional view of a system for controllingdeflection of a dynamic surface including a mating roll for creating nippressure, in accordance with further preferred embodiments of thepresent invention.

[0050]FIG. 14 shows a bottom view of the web support layer of FIG. 12having sensors and piezoelectric actuators connected thereto taken alonglines XIV-XIV of FIG. 12.

[0051]FIG. 15 shows the system of FIG. 12 after the dynamic surface hasreturned to an undeflected state.

[0052]FIG. 16 shows a side view of a system for controlling deflectionof a normally curved dynamic surface, in accordance with furtherpreferred embodiments of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0053] FIGS. 1A-3B show prior art rolls. Referring to FIG. 1A, the roll20 is a non-coated roll including an axle 22 loaded at its ends. Anon-coated roll generally includes rolls having metal tubes, such as asteel roll or tube. In contrast, a coated roll is understood to be aroll that is coated with a layer of flexible material such as rubber,fabric or cloth. The loading forces F are shown in FIG. 1. The forces F,together with the weight of the roll, provide the required nip pressureat the nip N formed by the interface of roll 20 and a mating roll 24.The forces shown in FIG. 1 and described above are dependent upon theposition of the roll 20 relative to the mating roll 24. For example,these forces would change if the roll 20 were under the mating roll 24(i.e., under the nip). The roll 20 includes a roll shell 26 that issecured about axle 22 via bearings 28. The roll shell has an interiorsurface 30 and an exterior surface 32. The longitudinal axis orcenterline of the axle 22 is indicated by A-A.

[0054]FIG. 1B shows another prior art non-coated roll 20′ that does nothave an axle extending therethrough as shown in FIG. 1A. The roll 20′includes a roll shell 26′ having an interior surface 30′ and an exteriorsurface 32′. The roll 20′ includes supports 22A′ and 22B′ that supportthe interior surface 30′ of the roll shell 26′ as the roll shell rotatesabout a longitudinal axis A′-A′. The supports 22A′ and 22B′ includesextensions 27′ supported by bearings 28′.

[0055]FIG. 2A shows a cross sectional view of the roll 20 and the matingroll 24 of FIG. 1A taken along line IIA-IIA of FIG. 1A. The roll 20 andmating roll 24 are designed for allowing a web 34 to pass therebetweenat the nip N. Mating rolls facilitate the development of nip pressuresbetween two rolls, thereby minimizing deflection of one or more rolls.Mating rolls, such as mating roll 24, may also be used as backup orsupport rolls. The roll 20 and the mating roll 24 may typically beincorporated into any assembly that processes a web of material such asa paper making assembly, a textile making assembly, a paper maker'sclothing making assembly, a printing assembly, a metal rolling assembly,an embossing assembly or a calendaring assembly.

[0056]FIG. 2B shows a cross-sectional view of the roll 20′ of FIG. 1Btaken along line IIB-IIB of FIG. 1B. The roll 20′ of FIG. 2B is asingular roll that is not in contact with a mating roll for creating nippressure.

[0057]FIG. 3A shows a simplified view of the roll 20 of FIGS. 1A and 2Ain a deflected orientation. The mating roll 24 may also deflect asindicated by the dashed lines. The deflection of the roll 20 may be theresult of deflecting forces applied to the exterior surface 32 of theroll by a web (not shown), and by gravity. FIG. 3B shows a simplifiedview of the roll 20′ of FIGS. 1B and 2B in a deflected state. The rolldeflection shown in FIGS. 3A and 3B can have detrimental effects on therolls, the machinery containing the rolls or the products being producedusing the rolls. The present invention is directed towards a controlsystem that both detects roll deflection anywhere on a roll and activelycorrects a deflection condition anywhere on the roll for rapidly andefficiently returning the roll to an undeflected state. In certainembodiments, it may be preferable to detect and/or correct rolldeflection only at the portion of the roll at the nip. To a broaderextent, the present invention is directed toward providing a controlsystem for a dynamic surface for detecting the occurrence of adeflection in a dynamic surface, measuring the magnitude of thedeflection, and then operating actuators to return the dynamic surfaceto an undeflected condition.

[0058]FIG. 4A shows a deflection control system 100 for a roll 102 inaccordance with certain preferred embodiments of the present invention.The roll 102 includes an axle 104 having bearings 106 for supporting aroll shell 108. The roll shown in FIG. 4A is commonly referred to as anon-coated roll. A non-coated roll is typically made by providing a rollshell, such as a solid steel shell, that supplies the main support forthe roll. The roll shell 108 has a longitudinal axis that issubstantially parallel to the longitudinal axis B-B of axle 104. Theroll shell 108 is generally cylindrical or tubular and includes an innersurface 110 defining an inner diameter and an exterior surface 112defining an outer diameter. The outer diameter (O.D.) of the roll 102 isdefined by the exterior surface 112 of roll shell 108.

[0059] The deflection control system also includes a plurality ofsensors 114 and a plurality of piezoelectric actuators 116 connected tothe interior surface 110 of the roll shell 108. The sensors 114 andpiezoelectric actuators 116 are in signal sending and receivingcommunication with a controller 118 via conductive traces 120 extendingbetween the sensors 114 and piezoelectric actuators 116, and thecontroller 118. For clarity of illustration, FIG. 4A shows only onesensor 114 and one piezoelectric actuator 116 connected to controller118, however, it should be understood that all of the sensors andactuators are preferably in signal sending and receiving communicationwith the controller. In the particular embodiment shown in FIG. 4A, thecontroller 118 is located within the roll 102 for rotatingsimultaneously with the roll, the sensors 114 and the piezoelectricactuators 116. Power for the controller may be provided from astationary power source 122 through a power line 123 that extendsthrough axle 104. The energy is transmitted from the stationary powersource to the rotating controller via a connection mechanism, such as aslip ring, that will not twist the power line 123. The controller 118preferably includes a microprocessor 124 and a memory device 126 forstoring a deflection control strategy or data related to preferredoperating conditions for the roll 102 and roll shell 108. The controller118 preferably uses one or more software applications stored thereincapable of receiving feedback signals from the sensors 114, comparingthe feedback signals with data stored in the memory device 126 andgenerating a series of output signals for transmission to thepiezoelectric actuators 116. Upon receiving the output signals, thepiezoelectric actuators are actuated for removing deflections in theroll shell 108, as will be described in more detail below.

[0060] In operation, a moving web (not shown) passes through a nip Ncreated by roll 102 and mating roll 130. The roll 102 and mating roll130 are shown in a generally horizontal orientation, however, thedeflection control system of the present invention is also intended foruse when the rolls 102, 130 have a substantially vertical orientation orany other geometric orientation. For clarity of illustration, FIG. 4Ashows two rolls: roll 102 and mating roll 130. However, the presentinvention may also be used for controlling deflections having three ormore rolls in contact with one another including a calendar stack ofrolls whereby at least one of the rolls in the stack has two or more nipsurfaces.

[0061]FIG. 4B shows a fragmentary view of a roll having a deflectioncontrol system in accordance with further preferred embodiments of thepresent invention. The FIG. 4B embodiment is substantially similar tothe embodiment shown in FIG. 4A, however, the FIG. 4B embodimentincludes a coated roll 102, having a roll shell 108′. The roll shell108′ includes a flexible coating 108A′ overlying a structural supportmember 108B′. The flexible coating preferably includes a flexiblematerial such as an elastomer (e.g. rubber) or cloth. When the flexiblematerial is an elastomer, the structural support member 108B′ ispreferably a solid tube, such as a steel tube. The outer diameter of thecoated roll 102′ is defined by the exterior surface 112′ of the flexiblecoating 108A′. Both the non-coated roll 102 of FIG. 4A and the coatedroll 102′ of FIG. 4B are dynamically flexible and include dynamicsurfaces as that term is defined herein. As a result, the rolls of FIGS.4A and 4B may deflect and/or vibrate during operation.

[0062]FIG. 4C shows another embodiment of the present invention havingthe sensors 114″ and piezoelectric actuators 116″ on the outer diameter112″ of the roll 102″. The roll 102″ is a coated roll including a rollshell 108″ including a flexible coating 108A″ overlying a structuralsupport member 108B″. The sensors 114″ and piezoelectric actuators 116″are on the exterior surface 112″ of the flexible coating 10BA″. Infurther embodiments, the roll may be a non-coated roll and the sensorsand actuators are provided on the exterior surface of the roll shell(i.e., the exterior surface of the structural support member).

[0063] Although the present specification provides a detaileddescription of the deflection control system of the present inventionwhen describing the roll 102 embodiment shown in FIG. 4A, the presentinvention is equally applicable to the coated roll 102′ embodiment shownin FIG. 4B, the roll 102″ embodiment shown in FIG. 4C, or any other typeof dynamic surface.

[0064]FIG. 5 shows a fragmentary view of FIG. 4A, taken along linesIV-IV, showing sensors 114 and piezoelectric actuators 116 connected tothe inner surface 110 of the roll shell 108. The piezoelectric actuators116 are preferably aligned in rows C, D, E, F, G, H and I that extendsubstantially parallel to the longitudinal axis B-B of the roll shell108. Each piezoelectric actuator 116 preferably has a length ofapproximately 1 to 5 centimeters, a width of approximately 1 to 5centimeters, and a height of less than one centimeter. Thus, eachpiezoelectric actuator 116 generally covers an area of approximately1-25 cm². The sensors 114 are interspersed between the piezoelectricactuators 116 and are preferably spaced so that the controller is ableto monitor the entire dynamic surface of the roll. The sensors aredesigned for detecting the presence of a deflecting force on the dynamicsurface of the roll shell 108. As used herein, the term “deflectingforce” may include any force that causes the dynamic surface of the rollto deflect, including a pressure force, a tensile force or a compressiveforce.

[0065] The number of piezoelectric actuators 116 generally outnumbersthe number of sensors 114 by a significant amount. In one preferredembodiment, the ratio of piezoelectric actuators to sensors isapproximately 100:1. Preferred sensors include piezoelectric elements,strain gauges, a laser and reflective element sub-assembly, an opticaldevice, a capacitive device, and/or a magnetic device. In the preferredembodiment shown in FIGS. 4A and 5, the sensors are piezoelectricelements capable of detecting a deflecting force on the dynamic surfaceof the roll. Such a deflecting force will cause the piezoelectric sensorto stretch or compress. The piezoelectric sensor will then transform thephysical movement into an electric signal, whereby the magnitude of theelectric signal is proportional to the magnitude of the physicalmovement of the sensor. The electric signal is the feedback signal thatis sent to the controller. The electric signal may be either an electricvoltage signal or a current signal.

[0066]FIG. 6 shows an enlarged fragmentary view of rows D, E and F ofFIG. 5. Each row includes a plurality of piezoelectric actuators 116with sensors 114 interspersed between the piezoelectric actuators. Thesensors 114 preferably monitor a specific region of the roll shell 108to detect whether that region is subjected to a deflecting force. Eachsensor 114 operates independently of one another. For example, sensor114 F in row F may detect a deflecting force while sensor 114E of row Edetects no deflecting force. The piezoelectric actuators may alsooperate independently of one another. For example, piezoelectricactuator 116F may apply a counter deflecting force to the roll shellwhile piezoelectric actuator 116E is not actuated and applies no counterforce to the roll shell. Moreover, piezoelectric actuators adjacent oneanother may apply counter forces having different magnitudes, e.g.piezoelectric actuator 116E applies a counter deflecting force having agreater magnitude that the force applies by piezoelectric actuator116E′. The actual magnitude of the counter force applied by any onepiezoelectric actuator is proportional to the magnitude of the electricsignal received from the controller 118 (FIG. 4). Although the actuators116 are depicted in rows, the present invention includes embodimentswhere the actuators are arranged randomly or in a pattern. The sensors114 may also be arranged in a pattern or randomly.

[0067] Referring to FIGS. 4A and 6, during operation or rotation of theroll 102, the region of the roll shell 108 overlying row D may be incontact with a moving web while regions of the roll shell overlying rowsE and F are not in contact with the web. As a result, the moving webdeflects the roll shell overlying row D while rows E and F remainundeflected. Thus, the sensors 114D in row D will detect a deflectingforce while the sensors 114E and 114F of respective rows E and F willnot detect a deflecting force. In response, output signals sent from thecontroller to piezoelectric actuators 116D of row D will physically movethose piezoelectric actuators for returning the dynamic surface of theroll shell 108 overlying actuators 116D to an undeflected state.However, no output signals will be sent to the piezoelectric actuators116E and 116F in rows E and F. As such, piezoelectric actuators willonly be activated by output signals when necessary to correctdeformation of the roll shell or when it is desirable to activelydeflect the dynamic surface of the roll shell. The force applied by eachactuator in any one row may vary. For example, the actuators in thecenter of a row may apply more compressive force than the actuatorsadjacent a journal. In addition, in any one row, the actuators adjacentone journal may provide more compressive force than the actuatorsadjacent an opposed journal.

[0068]FIGS. 7 and 8 show the roll 102 of FIG. 4A before activation ofthe deflection control system of the present invention. During operationof the roll, a web 128 (not shown in FIG. 7) passes between the roll 102and mating roll 130. The rotational speed of the roll 102 is dependentupon a number of factors including the speed of the web passing betweenroll 102 and mating roll 130 and the outer diameter of the roll.Referring to FIG. 8, in response to a number of deflecting forces,including web tension, nip pressure and gravity, the roll 102 and theroll shell 108 deform, placing an upper portion 132 of the roll shell108 under tension and the lower end 134 of the roll shell undercompression. Moreover, when the roll has a relatively high rate ofrotation (e.g., 5000 revolutions/minute), there are additional forcesacting upon the roll 102 and roll shell 108 including dynamic influencessuch as imbalance and modal excitation. As set forth above, rolldeflection is undesirable because it will have an adverse effect on thematerial 128 (e.g. a web) passing between the roll 102 and the matingroll 130.

[0069] Referring to FIGS. 7 and 8, the sensors 114B in the vicinity ofthe lower end 134 of the roll shell 108 are activated for detecting thatthe dynamic surface of the roll 102 is under compression and will sendfeedback signals to the controller (FIG. 4) relaying such information.The feedback signals generated by the sensors 114B near the ends 140A,140B of the roll shell 108 will have an intensity that is less than theintensity of the feedback signals generated by the sensors 114B′ nearthe middle 142 of the roll. Upon receiving feedback signals from thesensors 114B located at the bottom of the roll shell, the controllerwill determine that the lower portion of the roll shell is undercompression. The controller will then calculate output signals to besent to each of the piezoelectric actuators 116B located in the bottom134 of the roll shell. The magnitude of the output signals sent to theindividual piezoelectric actuators may vary. This is because the amountof correction required at the outer ends 140A, 140B of the roll may beless than the amount of correction required in the middle 142 of theroll. As a result, the magnitude of the signals sent to thepiezoelectric actuators 116B at the ends of the roll may be less thanthe magnitude of the signals sent to the piezoelectric actuators 116B′at the middle 142 of the roll. Upon receiving the output signals fromthe controller, the piezoelectric actuators 116 at the lower end 134 ofthe roll 108 will exert tensile forces on the dynamic surface of theroll for returning the lower end of the roll to a substantially flat,straight or undeflected orientation. As used herein, the term “flat” isdirected to a planar surface area on a roll having a length and a width.The term “straight” is directed to a straight line across the surface ofa roll having only one dimension. In certain embodiments, one or morepiezoelectric actuators may “max out”, i.e. a condition where thepiezoelectric actuator is exerting a maximum force and this maximumforce is not enough to completely remove a localized deflection in thedynamic surface. In these instances, piezoelectric actuators locatedoutside the area of the deflection may be actuated to assist the “maxedout” piezoelectric actuators.

[0070] Simultaneously, the sensors 114A and piezoelectric actuators 116Aat the upper end 132 of the roll are also operating in order to removeany deflections from the dynamic surface of the roll 108. Referring toFIGS. 7 and 8, the upper end 132 of the roll is under tension, with thesensors 114A′ located at the middle portion 144 of the roll detectinggreater tension than the sensors 114A at the outer ends 146A, 146B ofthe roll. Upon receiving feedback signals from the sensors 114A locatedat the upper end of the roll 108, the controller (FIG. 4) will determinethe magnitude of the output signals that must be sent to each of therespective piezoelectric actuators 116 in order to remove the deflectionfrom the dynamic surface at the upper end 132 of the roll 108.

[0071] Referring to FIG. 8, the piezoelectric actuators 116 and sensorsat the first and second sides 136, 138 of the roll 102 may beinactivated, while the piezoelectric actuators and sensors at the upperand lower ends of the roll remain activated. In other embodiments, thesensors may remain active at all times, however, the actuators may bedeactivated because removing deflections from the sides may beunnecessary or undesirable. Although the first and second sides 136, 138may be deflected, the roll at these locations is generally not understress or strain. Moreover, activating the piezoelectric actuators atsides 136, 138 may have little or no effect on correcting rolldeflection as depicted in the figures. thus, there is generally no needto send output signals to the piezoelectric actuators at the first andsecond sides 136, 138. Nevertheless, the sensors 114 located in thevicinity of the first and second sides 136, 138 continuously monitor thedynamic surface of the roll to detect deflecting forces acting upon thedynamic surface. In other preferred embodiments, the control strategymay include applying a tension force on one side of the roll andapplying a compression force on the opposite side of the roll, wherebythe applied tension and compression forces are approximately 180 degreesapart. In further embodiments, the control strategy may result intension forces being applied simultaneously to opposed sides of a roll.In still further embodiments, a tension or compression force may beapplied to one side of the roll while the actuators on the opposite sideof the roll remain inactive. This strategy may be used when it isdesirable to control roll deflection only when the dynamic surface ofthe roll is at the nip. Other preferred control strategies may includeactivating or deactivating opposed actuators in unison or separately.

[0072]FIG. 8 provides merely a “snap-shot” in time as the roll 102revolves about axle 104. It should be understood that the roll iscontinuously rotating and may rotate anywhere within a range ofapproximately 2 revolutions/hour to 5000 revolutions/minute. Thus, eachpiezoelectric actuator may continuously switch between active/inactivestates and/or tensile/compressive states many times each second. When anactuator is active, it may switch between tensile, neutral orcompressive states many times each second. The exact frequency forswitching between the various states depends upon the rotational speedof the roll which, in turn, depends upon the speed of the web and theouter diameter (O.D.) of the roll.

[0073] FIGS. 9A-9D show a simplified view of FIG. 8 showing one sensor114 and one piezoelectric actuator 116 during one complete revolution ofroll 102. In FIG. 9A the sensor 114 detects that the dynamic surface ofthe roll 108 is under compression. As a result, the sensor 116 measuresthe magnitude of the compression force and generates a feedback signalproportional to the magnitude of the compression force. Upon receivingthe feedback signal, the controller (FIG. 4) compares the magnitude ofthe feedback signal to data stored in the memory. The controller thencalculates how much tensile force must be exerted by piezoelectricactuator 116 upon the dynamic surface in order to return the roll to anundeflected condition. The controller then generates and transmits anoutput signal to the piezoelectric actuator 116 having a sufficientmagnitude for returning the dynamic surface to an undeflected condition.

[0074] The roll 102 continues to rotate until the sensor 114 andpiezoelectric actuator 116 reach the location shown in FIG. 9B. At thislocation, the dynamic surface may be undeflected so that the dynamicsurface is subjected to neither tensile nor compressive forces. As aresult, the feedback signal transmitted from the sensor 114 to thecontroller will indicate that there is no deflection. The controllerwill determine that there is no need to send a correcting signal to thepiezoelectric actuator 116. In other embodiments, the control strategyof the controller may be to deactivate the piezoelectric actuator 116when it is in the position shown in FIG. 9B. As a result, the controllerwill not send a correcting signal to the actuator 116, regardless ofwhether or not the sensor detects compression or deflection of the roll.

[0075] When the sensor 114 and the piezoelectric actuator 116 reach theposition shown in FIG. 9C, the sensor will detect tensile forces on theroll. The sensor 114 will transmit a feedback signal to the controldevice indicating that the dynamic surface is under tension. Inresponse, the controller will generate an output signal proportional tothe feedback signal for transmission to the piezoelectric actuator 116.Upon receiving the feedback signal, the piezoelectric actuator 116 willapply a compression force to the dynamic surface of the roll for urgingthe dynamic surface into a substantially undeflected orientation.

[0076] The roll continues to rotate until the sensor 114 and thepiezoelectric actuator 116 reach the position shown in FIG. 9D. In thisposition, there may once again be no compression or tensile forces uponthe dynamic surface of the roll. As a result, the sensor 114 willtransmit a feedback signal to the controller indicating that the dynamicsurface is substantially undeflected. Because there is no need to changethe shape of the dynamic surface, the controller will not transmit acorrecting signal to the piezoelectric actuator 116. As mentioned above,the roll shown in FIGS. 9A-9D will continue to revolve about the axle104 at a rate of approximately 2 revolutions/hour to 5000revolutions/minute. Thus, it is possible for the piezoelectric actuators116 to switch between active/inactive states and/or tensile/compressivestates, or any combination or series ofactive/inactive/tensile/neutral/compressive states thousands of timesper minute. Moreover, counter deflecting forces applied by eachpiezoelectric actuator may be precisely controlled by preciselycontrolling the magnitude of the electric signal sent to eachpiezoelectric actuator.

[0077]FIG. 10 shows the roll 102 of FIG. 7 after the deflection controlsystem has been activated. The dynamic surface 112 of the roll 108remains substantially undeflected during revolution of the roll eventhough deflecting forces continue to act upon the roll 108. The dynamicsurface 112 of the roll will remain undeflected as long as thedeflection control system continues to operate.

[0078]FIG. 11A shows a deflection control system 200 for a non-coatedroll 202 in accordance with further preferred embodiments of the presentinvention. The roll 202 includes a roll shell 208 having first andsecond ends 215A and 215B. The system includes first and second supports217A and 217B for supporting the first and second ends 215A and 215B ofthe roll shell 208. The supports 217A and 217B are connected with theinterior surface 210 of the roll shell 208 for supporting rotation ofthe roll 202. The supports 217A and 217B extend beyond the ends 215A and215B of the roll shell 208 to bearings 206 so that the roll 202 mayrotate about longitudinal axis C-C. The roll 202 includes a controller218 for controlling deflection of the roll shell 208. The controller 218is in communication with sensors 214 and piezoelectric actuators 216 viatraces 220. FIG. 11A shows only one sensor 214 and one piezoelectricactuator 216 connected to controller 218, however, it should beunderstood that all of the sensors and actuators are preferably insignal sending and receiving communication with the controller. Thecontroller 218 is preferably located within roll shell 208 for rotatingsimultaneously with the roll shell, the sensors 214 and thepiezoelectric actuators 216. Power for the controller 218 may beprovided from a power source 222 through a power line 223 that extendsthrough one of the structural members 217. The controller 110 operatesin a manner that is substantially similar to that described above inregards to FIG. 4A.

[0079]FIG. 11B shows another embodiment of the present invention that issubstantially similar to the FIG. 11A embodiment, however, the FIG. 11Bembodiment includes a coated roll 202′. The coated roll 202′ includes aroll shell 208′ having a flexible coating 208A′ surrounding structuralsupport member 208B′. The outer diameter of the coated roll 202′ isdefined by the exterior surface 212′ of the flexible coating 208A′. Boththe non-coated roll 202 of FIG. 11A and the coated roll 202′ of FIG. 11Bare dynamically flexible and include dynamic surfaces as that term isdefined herein. As a result, the non-coated and coated rolls disclosedherein may deflect and/or vibrate during operation.

[0080] FIGS. 12-15 show a deflection control system in accordance withfurther preferred embodiments of the present invention. Referring toFIG. 12, a web support element 300 is provided between two rolls 302 and304. The web support element supports a web 306 moving between firstroll 302 and second roll 304. Referring to FIG. 13A, the web supportelement 300 includes a web support layer 308 having a first surface 310for engaging the web 306 and a second surface 312 remote therefrom. Thesecond surface 312 of the web support layer 308 includes sensors 314 andpiezoelectric actuators 316 connected thereto. FIG. 13B shows anotherembodiment, similar to the embodiment of FIG. 13A, including a matingroll 330′, whereby a web 306, passes between the mating roll and the websupport layer 306′.

[0081] Referring to FIG. 14, in one preferred embodiment, the websupport layer 308 has a generally polygon shape and the piezoelectricactuators 316 are aligned in rows with sensors 314 interspersedtherebetween. The ratio of piezoelectric actuators to sensors isapproximately 100:1. The piezoelectric actuators and sensors may also bearranged in a pattern or randomly.

[0082]FIG. 13A shows the web support element 300 with the web supportlayer 308 being deflected downwardly by the web 306. As a result, thesecond surface 312 of the web support layer is under tension. As aresult, the sensors 314 in contact with the second surface 312 of theweb support layer 308 will transmit feedback signals to the controllerindicating that the web support layer is deflected. The controller willthen calculate the magnitude of the electrical signals that must be sentto each of the piezoelectric actuators 316 in order to return the websupport layer to an undeflected state. Upon receiving the outputsignals, the piezoelectric actuators 316 are actuated for applyingcompressive forces to the web support layer. The compression forces willreturn the web support layer 308 to the undeflected position shown inFIG. 15. The web support layer 308 shown in FIGS. 12-15 is substantiallyflat.

[0083]FIG. 16 shows other preferred embodiments of the present inventionwhereby the control strategy of the deflection control system seeks tomaintain the web support layer 408 in a predetermined shape. In onepreferred embodiment, the predetermined shape is the curved shape shownin FIG. 16. However, the predetermined shape may be any geometric shape.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.
 1. A methodof controlling deflection of a dynamic surface having a predeterminedshape comprising: (a) sensing a change in the predetermined shape of thedynamic surface; (b) providing at least one piezoelectric actuator incommunication with the dynamic surface for applying a counter forcethereto; and (c) activating said at least one piezoelectric actuator forapplying the counter force to the dynamic surface for returning thedynamic surface to the predetermined shape.
 2. The method as claimed inclaim 1 , wherein the sensing step includes providing at least onesensor in communication with the dynamic surface.
 3. The method asclaimed in claim 2 , wherein said at least one sensor is in contact withthe dynamic surface.
 4. The method as claimed in claim 2 , wherein theapplying step includes providing a controller in communication with saidat least one sensor and said at least one piezoelectric actuator.
 5. Themethod as claimed in claim 4 , further comprising transmitting afeedback signal from said at least one sensor to said controller afterthe sensing step.
 6. The method as claimed in claim 5 , wherein theactivating step includes: generating an output signal at said controllerupon receiving said feedback signal; and transmitting the output signalto said at least one piezoelectric actuator.
 7. The method as claimed inclaim 1 , wherein said at least one piezoelectric actuator includes aplurality of piezoelectric elements in contact with the dynamic surface,said plurality of piezoelectric elements being aligned in a series ofrows, the method further comprising activating a first row of saidpiezoelectric actuators and deactivating a second row of saidpiezoelectric actuators.
 8. The method as claimed in claim 7 , whereinthe first row of said piezoelectric actuators is activated while thesecond row of piezoelectric actuators is inactive.
 9. The method asclaimed in claim 7 , wherein the first row of said piezoelectricactuators is adjacent to the second row of piezoelectric actuators. 10.The method as claimed in claim 1 , wherein the activating step includesapplying a compressive force to the dynamic surface.
 11. The method asclaimed in claim 1 , wherein the activating step includes applying atensile force to the dynamic surface.
 12. The method as claimed in claim1 , wherein the activating step includes applying a compressive forceand a tensile force to the dynamic surface.
 13. The method as claimed inclaim 9 , further comprising: passing a web over the dynamic surface;and selectively activating and deactivating adjacent rows of saidpiezoelectric actuators during the passing step so as to return thedynamic surface to said predetermined shape.
 14. A method forcontrolling a dynamic surface having a shape comprising: providing atleast one piezoelectric element in contact with the dynamic surface; andactivating said at least one piezoelectric element for applying a forceto the dynamic surface so as to change the shape of the dynamic surface.15. The method as claimed in claim 14 , further comprising providing aroll having a roll shell including the dynamic surface.